In order to meet the demand for wireless data traffic, which has been increasing since the commercialization of a fourth-generation (4G) communication system, efforts are being made to develop an improved fifth-generation (5G) communication system or pre-5G communication system. For this reason, a 5G communication system or pre-5G communication system is referred to as a beyond-4G-network communication system or a post-LTE system.
To achieve a high data transmission rate, implementing a 5G communication system in an extremely high frequency (mmWave) band (for example, a 60 GHz band) is being considered. To relieve the path loss of radio signals and to increase the transmission distance of radio signals in an extremely high frequency band, beamforming, massive Multiple-Input and Multiple-Output (massive MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, analog beamforming, and large scale antenna techniques are under discussion for a 5G communication system.
Further, to improve the network of the system, technical development in an evolved small cell, an advanced small cell, a cloud Radio Access Network (cloud RAN), an ultra-dense network, Device to Device (D2D) communication, wireless backhaul, a moving network, cooperative communication, Coordinated Multi-Points (CoMP), and interference cancellation is progressing for the 5G communication system.
In addition, an Advanced Coding Modulation (ACM) scheme including Hybrid FSK and QAM modulation (FQAM) and Sliding Window Superposition Coding (SWSC) as well as an advanced access technique including Filter Bank Multi Carrier (FBMC), Non-Orthogonal Multiple Access (NOMA), and Sparse Code Multiple Access (SCMA) are being developed for the 5G system.
In the downlink of an LTE-based system, a reference signal common to all cells, that is, a Common Reference Signal (CRS), is defined. A CRS may be used not only for the demodulation of data channel signals but also for the measurement of downlink channel quality for scheduling, that is, a Channel Quality Indicator (CQI), for cell search and the estimation of a downlink channel state (measurement of mobility) in handover.
An LTE Advanced (LTE-A) system further defines, in addition to a CRS, a Channel State Information Reference Signal (CSI-RS) that is dedicated to CQI measurement. A CSI-RS may support CQI measurement for a plurality of cells and may be used to achieve the transmission of data channel signals by a plurality of cells. A CRS is used for the CQI measurement of a serving cell, while a CSI-RS may be used for the CQI measurement of neighboring cells.
A terminal determines a channel state for calculating CQI to be reported on uplink based on a CSI-RS and feeds back CSI including the CQI to a network. The CSI may include at least one of the following pieces of information in order to provide information on the channel state to the network.                Channel Quality Indicator (CQI)        Precoding Matrix Indicator (PMI)        Precoding Type Indicator (PTI)        Rank Indicator (RI)        
For a User Equipment (UE), CSI is mainly for estimating channel quality and for recommending to a network an appropriate precoding matrix (that is, precoder) to be used for actual transmission. In LTE, sets of various precoding matrices, that is, codebooks, which can be used in different transmission environments, are defined to report a precoding matrix. Unlike in codebook-based precoding, codebooks in non-codebook-based CSI reporting are used only for CSI computation at a UE and are not used for actual transmission.